ENG-2257 Add an existing discourse relation from relation menu

[trangdoan982]

https://entire.io/gh/DiscourseGraphs/discourse-graph/trails/32

Reviewer brief

• Result: "Add existing…" in the canvas relation type menu opens a picker in the same menu. Picking a type links it to the arrow's node-type pair (source → target), saves settings, shows the type in the menu and shows a "Discourse relation added" toast. The user then picks it to create the relation, as in the DES-349 Case 1 mockup.
• Review focus: associateRelationTypeWithNodePair in relationTypeUtils.ts is the shared helper ENG-2258 will call after adding a new type. It replaces the discourseRelations array, and the dropdown's memos depend on that array's identity to refresh the menu.
• Stacked on ENG-2256 Implement new relation menu empty state #1491 (ENG-2256); review only the commits after it.

Verification

• pnpm ci:validate --filter=@discourse-graphs/obsidian passes; new unit tests in src/components/canvas/utils/__tests__/relationTypeUtils.test.ts.
• Live Obsidian run with dg-obsidian-cdp-verify on the ENG-2256 fixture canvas:

Scenario	Result
Empty pair: Add existing… → pick first row	Picker listed all 4 accepted types; menu then showed "supports"; toast "supports relation added for Question and Claim"; data.json gained one rel3_ Question → Claim triple with no status
Then click the new type	Arrow got that relation type and the text "supports"
Populated pair (Evidence → Claim)	Picker listed only informs and derived from; flyout closed
Escape, then back chevron	Both returned to the list with the menu and pending arrow kept
Every type already valid for the pair	Picker shows "All relation types are already available for these nodes"

The failed-save error toast is covered by a unit test for the rollback only, not a live run.

Loom video

https://www.loom.com/share/d904ad974c9e4194bb0ff3e937fa7f4c

Scope check

• Ran $scope-check against the ENG ticket and final diff.
• Scope beyond Done When: The picker offers only accepted types not yet valid for the pair in either direction (the mockup lists all types). A back chevron and Escape return from the picker to the list. A failed save restores the in-memory settings and shows an error toast. RelationTypeDropdown takes a canvasPath prop for the toast target. These keep the picker from offering no-op picks, avoid a dead end that would delete the pending arrow, and keep the menu from showing an unsaved association. Decided with the requester during planning; recorded on ENG-2257 and DES-349.

Standards check

• Ran $dg-pr-adherence-check against the final diff and PR metadata.

Outstanding: the new markup uses the file's existing Tailwind gray utilities rather than Obsidian CSS variables, kept for consistency within the file.

Local delegated full review

• Ran a comprehensive review of the entire final diff in a subagent with a fresh context. Use $dg-delegated-full-review when no other full-review workflow is available.

No findings.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated
discourse-graph	Ready	Preview	Oct 2, 2026 8:58pm UTC

[linear-code]

ENG-2257

[devin-ai-integration]

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